Stoichiometric air/fuel ratio of gasoline vapor

[Michael Vannozzi]

Hello, Can someone tell me the optimum stoichiometric air/fuel ratio of gasoline VAPOR? I know that with liquid gasoline the optimum stoichiometric air/fuel ratio is 14.7 parts ambient air to 1 part gasoline. Thank you in advance for your help.

 

[SteamKing]

Hello, Can someone tell me the optimum stoichiometric air/fuel ratio of gasoline VAPOR? I know that with liquid gasoline the optimum stoichiometric air/fuel ratio is 14.7 parts ambient air to 1 part gasoline. Thank you in advance for your help.

Why do you think the ratio for gasoline vapor would be any different for liquid gasoline? It's all the same stuff.

 

[Michael Vannozzi]

Thank you for responding.The gasoline is heated and turned from a liquid into a fully gaseous state. The commonly accepted stoichiometric atmospheric air to atomized liquid gasoline ratio is 14.7 to 1. Typically, converting liquid gasoline to a gaseous state leans out the air fuel mixture in an internal combustion engine.
I am conferring with you and the Physics Forums to determine if there would be a change in the stoichiometric ratio if liquid gasoline is converted into Gasoline vapor. Kind regards, Michael Vannozzi

 

[SteamKing]

Thank you for responding.The gasoline is heated and turned from a liquid into a fully gaseous state. The commonly accepted stoichiometric atmospheric air to atomized liquid gasoline ratio is 14.7 to 1. Typically, converting liquid gasoline to a gaseous state leans out the air fuel mixture in an internal combustion engine.
I am conferring with you and the Physics Forums to determine if there would be a change in the stoichiometric ratio if liquid gasoline is converted into Gasoline vapor. Kind regards, Michael Vannozzi

You can't burn liquid gasoline in an engine. The carburetor/fuel injection system atomizes the liquid gasoline into vapor so that it can mix easily with the combustion air.

I don't know what you mean by "Typically, converting liquid gasoline to a gaseous state leans out the air fuel mixture in an IC engine." This can only happen if some of the gasoline vapor is lost to the atmosphere before it enters the engine, or if your engine is running with some percentage of excess air, above the amount required for combustion.

https://en.wikipedia.org/wiki/Air–fuel_ratio

 

[Michael Vannozzi]

Atomization of a liquid means that liquid is segmented into tiny droplets, but it is still in liquid form. You are correct in your statement that liquid gasoline doesn't burn. Only that small percentage of the atomized gasoline that comes into contact with the heated surfaces of the top of the hot piston, the hot bottom of the intake manifold tract, and the engineered overlap of the camshaft that allows the exhaust valve to be open for a split second at the end of the exhaust stroke while simultaneously, the Intake valve starts to open, allowing intimate contact between a residue of hot exhaust gases and the intake charge of atmospheric air and an atomized gasoline mixture. This system converts only a small portion,(20-30%), of the atomized gasoline into a vapor or true gaseous state, which in turn is consumed by the internal combustion process of the engine. My question is: are you saying conclusively that the stoichiometric ratio of atmospheric air to gasoline ratio does not change when liquid gasoline is converted from a liquid into a gas,(vapor)?

 

[SteamKing]

Atomization of a liquid means that liquid is segmented into tiny droplets, but it is still in liquid form. You are correct in your statement that liquid gasoline doesn't burn. Only that small percentage of the atomized gasoline that comes into contact with the heated surfaces of the top of the hot piston, the hot bottom of the intake manifold tract, and the engineered overlap of the camshaft that allows the exhaust valve to be open for a split second at the end of the exhaust stroke while simultaneously, the Intake valve starts to open, allowing intimate contact between a residue of hot exhaust gases and the intake charge of atmospheric air and an atomized gasoline mixture. This system converts only a small portion,(20-30%), of the atomized gasoline into a vapor or true gaseous state, which in turn is consumed by the internal combustion process of the engine. My question is: are you saying conclusively that the stoichiometric ratio of atmospheric air to gasoline ratio does not change when liquid gasoline is converted from a liquid into a gas,(vapor)?

Not unless you have a leak somewhere in your intake system.

Read the article I attached about air-fuel ratios

 

[Michael Vannozzi]

Will do. Thanks, Mike

 

[Mech_Engineer]

Correct me if I'm wrong, but it's my understanding the stoichiometric air/fuel ratio is a mass ratio, in which case it doesn't matter whether the gasoline is in a vapor or gaseous state because the mass will be equivalent regardless of phase...

 

[Michael Vannozzi]

You can't burn liquid gasoline in an engine. The carburetor/fuel injection system atomizes the liquid gasoline into vapor so that it can mix easily with the combustion air.

I don't know what you mean by "Typically, converting liquid gasoline to a gaseous state leans out the air fuel mixture in an IC engine." This can only happen if some of the gasoline vapor is lost to the atmosphere before it enters the engine, or if your engine is running with some percentage of excess air, above the amount required for combustion.

https://en.wikipedia.org/wiki/Air–fuel_ratio

Referring to this article, the lean situation in pre-vaporized gasoline probably occurs, because of a perfect stoichiometric ratio prior to the air/fuel mixture entering into the intake manifold of the engine. In a normal carbureted or fuel injected engine, their could be an engineered imbalance in the mixture of atmospheric air and atomized gasoline droplets, where only a small percentage of atomized gasoline are then converted into gasoline vapor to run the engine. Possibly the percentage of atomized gasoline droplets are engineered to be "over-supplied", creating an overly rich fuel curve, and therefore an inefficiency. This extra un-burnt gasoline, aka Hydrocarbons, are mixed with a secondary source of atmospheric air from an air injection pump, and then flows to the catalytic converter to be re-burned.

 

[SteamKing]

Referring to this article, the lean situation in pre-vaporized gasoline probably occurs, because of a perfect stoichiometric ratio prior to the air/fuel mixture entering into the intake manifold of the engine. In a normal carbureted or fuel injected engine, their could be an engineered imbalance in the mixture of atmospheric air and atomized gasoline droplets, where only a small percentage of atomized gasoline are then converted into gasoline vapor to run the engine. Possibly the percentage of atomized gasoline droplets are engineered to be "over-supplied", creating an overly rich fuel curve, and therefore an inefficiency. This extra un-burnt gasoline, aka Hydrocarbons, are mixed with a secondary source of atmospheric air from an air injection pump, and then flows to the catalytic converter to be re-burned.

It's generally not a good idea to dump raw gasoline into a catalytic converter to be burned. The catalyst is already operating at high temperature and doesn't need any additional heat.

Engines fitted with converters also carry quite a few different engine controls to make sure that at whatever operating condition the engine is running, the proper AF ratio can be looked up in a stored AF ratio map. The engine controls use this AF ratio data to adjust the metering of the fuel. Oxygen sensors in the exhaust stream help determine if the AF ratio is too lean or too rich, and fuel metering is also adjusted accordingly.

https://en.wikipedia.org/wiki/Oxygen_sensor

 

[Mech_Engineer]

Referring to this article, the lean situation in pre-vaporized gasoline probably occurs, because of a perfect stoichiometric ratio prior to the air/fuel mixture entering into the intake manifold of the engine.

But the mass of the fuel stays the same regardless of whether its vaporized or droplet, and the 14.7:1 ratio is a mass ratio.

In a normal carbureted or fuel injected engine, their could be an engineered imbalance in the mixture of atmospheric air and atomized gasoline droplets, where only a small percentage of atomized gasoline are then converted into gasoline vapor to run the engine. Possibly the percentage of atomized gasoline droplets are engineered to be "over-supplied", creating an overly rich fuel curve, and therefore an inefficiency. This extra un-burnt gasoline, aka Hydrocarbons, are mixed with a secondary source of atmospheric air from an air injection pump, and then flows to the catalytic converter to be re-burned.

As mentioned previously, fuel injected engines utilize oxygen sensors to control the fuel delivery, trying to maintain the correct AFR. For most operating conditions a typical ECU will aim for 14.7:1, although its common to increase fuel delivery to about 12.0:1 for wide open throttle to increase power.

 

[Michael Vannozzi]

It's generally not a good idea to dump raw gasoline into a catalytic converter to be burned. The catalyst is already operating at high temperature and doesn't need any additional heat.

Engines fitted with converters also carry quite a few different engine controls to make sure that at whatever operating condition the engine is running, the proper AF ratio can be looked up in a stored AF ratio map. The engine controls use this AF ratio data to adjust the metering of the fuel. Oxygen sensors in the exhaust stream help determine if the AF ratio is too lean or too rich, and fuel metering is also adjusted accordingly.

https://en.wikipedia.org/wiki/Oxygen_sensor

Yes, but the fact remains that a portion of gasoline does go unburned in modern gasoline internal combustion engines, despite the computerized controls, and any unburned hydrocarbons are then re-burned a second time by the catalytic converter to support cleaner exhaust emissions. This represents waste and inefficiency. The real problem is that gasoline cannot be completely vaporized and combusted in the cylinder in the milliseconds of time during the compression stroke. Their is simply not enough time to burn all of the gasoline.

 

[SteamKing]

Yes, but the fact remains that a portion of gasoline does go unburned in modern gasoline internal combustion engines, despite the computerized controls, and any unburned hydrocarbons are then re-burned a second time by the catalytic converter to support cleaner exhaust emissions. This represents waste and inefficiency. The real problem is that gasoline cannot be completely vaporized and combusted in the cylinder in the milliseconds of time during the compression stroke. Their is simply not enough time to burn all of the gasoline.

And yer point is ... ?

The various inefficiencies of the gasoline engine are well known.

 

[Mech_Engineer]

Yes, but the fact remains that a portion of gasoline does go unburned in modern gasoline internal combustion engines, despite the computerized controls, and any unburned hydrocarbons are then re-burned a second time by the catalytic converter to support cleaner exhaust emissions. This represents waste and inefficiency. The real problem is that gasoline cannot be completely vaporized and combusted in the cylinder in the milliseconds of time during the compression stroke. Their is simply not enough time to burn all of the gasoline.

I think you may be overestimating the amount of unburned gasoline being exhausted, do you have any publications or references which quantify how much gas is leftover after the combustion cycle?

http://www.explainthatstuff.com/catalyticconverters.html

Typically, there are two different catalysts in a catalytic converter:

• One of them tackles nitrogen oxide pollution using a chemical reaction called reduction (removing oxygen). This breaks up nitrogen oxides into nitrogen and oxygen gases (which are harmless, because they already exist in the air around us).
• The other catalyst works by an opposite chemical process called oxidation (adding oxygen) and turns carbon monoxide into carbon dioxide. Another oxidation reaction turns unburned hydrocarbons in the exhaust into carbon dioxide and water.

 

[Kevin McHugh]

The real problem is that gasoline cannot be completely vaporized and combusted in the cylinder in the milliseconds of time during the compression stroke. Their is simply not enough time to burn all of the gasoline.

That would be the power stroke (not to nitpick).

 

[Michael Vannozzi]

I think you may be overestimating the amount of unburned gasoline being exhausted, do you have any publications or references which quantify how much gas is leftover after the combustion cycle?

http://www.explainthatstuff.com/catalyticconverters.html

Yes, I do, Mech_Engineer. Here are a few:

http://www.consumerenergycenter.org/transportation/consumer_tips/vehicle_energy_losses.html

https://www.fueleconomy.gov/feg/atv.shtml

http://ffden-2.phys.uaf.edu/102spri...tes/zach's web project folder/eice - main.htm

Thanks for your interest.
Kind regards,
Michael Vannozzi

 

[Mech_Engineer]

None of those references specify the percentage of unburned fuel which is exhausted as a result of incomplete combustion. Try again.

I agree that overall combustion engines have relatively low efficiency, but the #1 loss is heat loss (radiator & exhaust), not unburned fuel.

 

[Michael Vannozzi]

The "EXHAUST LOSS" is the point. The majority of the un-burnt fuel is expelled through the "EXHAUST" port as the piston moves upward on the exhaust stroke, it expels the un-burnt fuel, along with the exhaust gasses from the burning/expansion process. Also, some of the un-burnt fuel mixed with carbon from the combustion process, and then it mixes in with the motor oil, in the gap between the compression rings, and this is what turns your engine oil black.
That un-burnt Gasoline is not used to propel the vehicle, therefore, you have the inefficiency.

 

[Mech_Engineer]

The exhaust loss is mainly thermal in nature, with some kinetic loss as well due to pumping the air. There is a negligible amount of fuel in it as long as the engine is running at peak combustion efficiency (e.g. Stoichiometric ratio). See here:

https://en.m.wikipedia.org/wiki/Exhaust_heat_recovery_system

Inside the exhaust pipe of an internal combustion engine, energy losses are various: thermal, kinetic, chemical and latent heat. Most important energy parts are located in the thermal and kinetic losses, the two others are negligible.

 

[Michael Vannozzi]

Hello again Mech_Engineer,
Thank you for taking the time to talk to me, appreciated. Just to let you know what I am doing, I am in the process of building a Gasoline Vapor System for an automobile, (1978 Chevy Camaro, 350 cu.in. SBC, automatic), I am on my 9th prototype and I am getting very close to success. The system does work and run.
I am using a stainless steel Shell & Tube Heat Exchanger, (3" X 14"), and I have plumbed exhaust tubes into the shell sides, with the system having it's own independent exhaust system. I am using a motorcycle carburetor to supply air and fuel. The Air/Fuel mixture flows through the 30 straight tubes, and then through a 2.5" 90,(elbow), into the Open Plenum Edelbrock intake manifold. The Stoichiometric ratio remains mostly in the 14:7 range, but goes down to the 12:1 range at lower RPM, (by Air/Fuel Gauge). I have been doing a lot of studying and research, and it seems that their are many of my predecessor's who believe that the 14.7:1 Stoichiometric is not correct for Vaporized Gasoline, and should be much leaner. What are your thoughts? Thanks, Mike

 

[Mech_Engineer]

Michael, I'm afraid it appears to me you've been the victim of a hoax and / or bad information. Vaporizing gasoline is not going to help the efficiency of your engine, it instead makes it harder to get the appropriate mass of gasoline in the cylinder for combustion (and potentially is very dangerous if you are in fact boiling the gasoline to make it into a vapor).

This is actually a new hoax to me, but a quick search on Google made it clear to me that the alleged "conspiracy" regarding gasoline vapor engines runs about as deep as "water engines." There are alleged 1970's cover-ups, hoax YouTube videos, all of it is very similar to other theories to increase engine efficiency that the "oil companies don't want you to know."

Have you considered just how you plan to prove the effectiveness of your system? Your measurement of the AFR isn't a measurement of the stoich. ratio, it's the real-time amount of fuel being burned in the engine. The fact that AFR is 12:1 in the lower RPM range means you're running a rich mixture.

 

[Mech_Engineer]

I have been doing a lot of studying and research, and it seems that their are many of my predecessor's who believe that the 14.7:1 Stoichiometric is not correct for Vaporized Gasoline, and should be much leaner. What are your thoughts?

Additionally, as far as I can tell this claim is bunk. The experimentally-derived stoich. ratio for gasoline is a mass ratio; given a certain mass of gasoline (it's a mixture of many molecules) and air (oxygen) it takes 14.7 pounds of air to combust 1 pound of gasoline. Mass is neither created nor removed as a result of a phase change, so regardless of whether the gasoline is tiny liquid droplets or gaseous vapor (or a combination of the two) the stoich. ratio for combustion should remain the same. Any claims to the contrary will need to provide experimental DATA (e.g. real-world proof), not philosophical arguments or YouTube videos.

 

[Michael Vannozzi]

Hello Again Mech_Engineer,
Thanks for your response, though I do not agree with you. As pointed out previously in this topic, Liquid Gasoline doesn't burn, only Gasoline Vapor Burns in a Gasoline powered internal combustion engine. The inefficiency lies in the gasoline that does not become vaporized, and therefore is not combusted. Their is simply not enough time in the milliseconds of the power stroke, to completely burn a atomized gasoline / air mixture that must be converted into vapor from the heat that exists in the combustion chamber in order to combust. It is a fact that gasoline engines are very inefficient, and waste fuel through various different ways. This wasted Gasoline not only represents inefficiently, and less power, it is a major cause of air pollution. It is possible to create a safe mechanical system to pre-vaporize Gasoline in the area of the Intake Manifold, and through engine vacuum, duct the Gasoline Vapor into the combustion chamber of the engine. It has been done successfully many times before. I would also respectfully disagree with you regarding the transport of liquid gasoline through the intake tract, while simultaneously keeping the air / liquid in suspension. This as opposed to moving a gas,(vapor) through the intake tract. In my opinion, moving a gas,(vapor) would be no different than simply moving only the air. May I also point out the existence of successful vehicles that currently run, on a daily basis, on Compressed Natural Gas and on Propane.
Regards, Mike

 

[Mech_Engineer]

Michael I'm afraid this thread won't have long to live if you continue to ignore the sound arguments being presented. I'll address your points one at a time:

As pointed out previously in this topic, Liquid Gasoline doesn't burn, only Gasoline Vapor Burns in a Gasoline powered internal combustion engine. The inefficiency lies in the gasoline that does not become vaporized, and therefore is not combusted.

Fuel injectors (and carburetors) are designed to atomize fuel in order to allow combustion. Since carburetors do not provide closed-loop control of fuel mix we will ignore them and focus on EFI systems.

When talking about electronic fuel injection (EFI) the atomized fuel is well-mixed and only makes up about 6% of the mixture by mass. When combusting at the stoichiometric ratio there is none left at the end of the combustion stroke (according to this reference, left-over hydrocarbons make up less than 0.25% of exhaust gases by mass). Your claims that fuel injectors do not allow for complete fuel atomization (and therefore incomplete combustion) are unfounded.

Their is simply not enough time in the milliseconds of the power stroke, to completely burn a atomized gasoline / air mixture that must be converted into vapor from the heat that exists in the combustion chamber in order to combust.

How have you determined there is not enough time? Provide a reference or calculation. As we all know, fuel-injected gasoline engines are pervasive these days, and they all obviously run very well.

It is a fact that gasoline engines are very inefficient, and waste fuel through various different ways. This wasted Gasoline not only represents inefficiently, and less power, it is a major cause of air pollution.

The main efficiency loss for an internal combustion engine is heat loss through the radiator and exhaust (approximately 60%). I have have provided references corroborating this fact.

Additionally, the provided reference shows that unavoidable combustion inefficiency losses account for about a 3.4% reduction in overall efficiency. This means that based on this paper your system can AT BEST provide a 3.4% increase in efficiency.

Unavoidable combustion inefficiency losses occur since not all of chemical energy supplied is released during the combustion process. Incomplete combustion products in the exhaust representing chemical energy not released during combustion accounted for 3.4% of the total fuel energy losses.

It is possible to create a safe mechanical system to pre-vaporize Gasoline in the area of the Intake Manifold, and through engine vacuum, duct the Gasoline Vapor into the combustion chamber of the engine. It has been done successfully many times before.

You need to provide one or more legitimate reference(s) proving this fact. YouTube videos and crackpot websites don't count.

I would also respectfully disagree with you regarding the transport of liquid gasoline through the intake tract, while simultaneously keeping the air / liquid in suspension. This as opposed to moving a gas,(vapor) through the intake tract. In my opinion, moving a gas,(vapor) would be no different than simply moving only the air.

What are you basing your disagreement on? I have seen no facts presented on your side to prove any of your claims...

May I also point out the existence of successful vehicles that currently run, on a daily basis, on Compressed Natural Gas and on Propane.

Irrelevant, we are addressing your specific assertion that you can achieve large efficiency gains in a gasoline engine by vaporizing the gasoline into gaseous form before combusting.

 

[Michael Vannozzi]

Have you considered just how you plan to prove the effectiveness of your system? Your measurement of the AFR isn't a measurement of the stoich. ratio, it's the real-time amount of fuel being burned in the engine. The fact that AFR is 12:1 in the lower RPM range means you're running a rich mixture.

Good Morning Mech_Engineer,

Yes, I have considered this. I am monitoring 6 aspects of the running engine: 1) Monitoring the real time Air/Fuel Ratio through a wideband Air/Fuel Ratio gauge, to keep it within the stoichiometric range 2) Monitoring the temperature of the Air/Fuel mixture flow entering the intake manifold using a Pyrometer gauge, and comparing it to the boiling rate of gasoline,(100 to 400 degrees Fahrenheit with a target temp. of @ 180 degrees. 3) A visual inspection of the flow of the Air/Fuel through a "Site Glass Port" in the tube from the Heat Exchanger where it enters the intake manifold 4) Monitoring the temperature of the exhaust manifolds, diverter tubes, and the heat exchanger through a laser pointer temperature meter gun. 5) A smog test by an independent 3rd party testing company. 6) A comparison of the current Gas mileage of the automobile as opposed to the factory ratings, with a goal of quadrupling the factory gas mileage ratings.

Yes, regarding the 12:1 A/F ratio reading, this varies between the 12:1 and 15:1 as the engine is running, and at different engine R.P.M. levels. I am aware of and monitoring the real time lean / rich state of the gasoline, in comparison to the known stoichiometric ratio of gasoline.

Thank you for your interaction and debate, it is stimulating!
Kind regards, Mike

 

[Mech_Engineer]

Let me put it this way- how are you calculating the efficiency of the engine with your contraption on it, and how will you compare that to "normal" operation?

 

[Michael Vannozzi]

Hello again,
First of all, you keep referring back to a computer controlled, electronic fuel injected engine, and I am working on a 1978 Camaro with a 350 cu. in. V8 and a carburetor. You are trying to compare Apples and Oranges, and the data that you supply reflects such. Also, I am not writing a paper here for college here, I am an older man, and I simply do not have the time to keep arguing back and forth with you., I am to busy for that. I have my own thoughts and theories, and am implementing them and testing them for my own reasons and on my own dime, as is my prerogative. I came to this forum to enquire about a simple question that I had regarding the Stoichiometric ratio of liquid Gasoline vs. Gasoline Vapor, and I received my answer from you and others. But I will leave you with one final point, Atomized gasoline is simply small fragments of liquid gasoline, and is not Gasoline Vapor. Atomized Gasoline is emulsified with atmospheric air, through the carburetors Venturi, and does not turn to Gasoline Vapor until it is HEATED in the combustion chamber, where it is then ignited and combusted. It is a commonly known fact that un-combusted liquid gasoline, mixed with carbon from the combustion process remains after the completion of the power stroke, and it is this inefficiency that I am working on.

 

[Mech_Engineer]

you keep referring back to a computer controlled, electronic fuel injected engine, and I am working on a 1978 Camaro with a 350 cu. in. V8 and a carburetor. You are trying to compare Apples and Oranges, and the data that you supply reflects such.

You have claimed specifically in this thread that carburated and fuel-injected engines are not able to fully combust the fuel mixture. The publications provided prove this is not the case on the fuel-injected side at very least. Most of the arguments apply for a carburetor as well however (assuming a well-dispersed fuel mixture from the carburetor's jets). For a well-mixed air/fuel mixture running at an AFR of 14.7, there will be almost no fuel left in the exhaust after combustion.

I have my own thoughts and theories, and am implementing them and testing them for my own reasons and on my own dime, as is my prerogative.

That's fine, but I've provided enough information here for you to understand why it doesn't work after you've completed your experiments.

It is a commonly known fact that un-combusted liquid gasoline, mixed with carbon from the combustion process remains after the completion of the power stroke, and it is this inefficiency that I am working on.

You keep claiming this but have provided no real data regarding how much is left (and therefore how much potential benefit your system would provide). Additionally you're claiming you will achieve 100% combustion of the fuel but my understanding is there are certain fundamental limitations in a combustion cycle which prevent 100% perfect burning of a fuel, have you taken this into consideration?

If your claim is "commonly known" then it should be easy to find a publication with a simple Google search which reinforces this claim. I've provided references that show there is very little gas left when running at the correct AFR; this tells me even if you could combust the last few percent of gasoline it would at best result in a negligible increase in efficiency.

 

[Randy Beikmann]

Hello again,
First of all, you keep referring back to a computer controlled, electronic fuel injected engine, and I am working on a 1978 Camaro with a 350 cu. in. V8 and a carburetor. You are trying to compare Apples and Oranges, and the data that you supply reflects such. Also, I am not writing a paper here for college here, I am an older man, and I simply do not have the time to keep arguing back and forth with you., I am to busy for that. I have my own thoughts and theories, and am implementing them and testing them for my own reasons and on my own dime, as is my prerogative. I came to this forum to enquire about a simple question that I had regarding the Stoichiometric ratio of liquid Gasoline vs. Gasoline Vapor, and I received my answer from you and others. But I will leave you with one final point, Atomized gasoline is simply small fragments of liquid gasoline, and is not Gasoline Vapor. Atomized Gasoline is emulsified with atmospheric air, through the carburetors Venturi, and does not turn to Gasoline Vapor until it is HEATED in the combustion chamber, where it is then ignited and combusted. It is a commonly known fact that un-combusted liquid gasoline, mixed with carbon from the combustion process remains after the completion of the power stroke, and it is this inefficiency that I am working on.

Mike, Mech_Engineer is completely right. I will say that most of the time, only about 1% - 2% of fuel goes unburned in an engine (this is covered in Heywood's book "Internal Combustion Engine Fundamentals"). So any effort someone makes to improve efficiency by "burning all that unburned fuel in the exhaust" would only improve gas mileage from say, 20 mpg to 20.4 mpg - even if you could do it!

Carbureted engines aren't as efficient as today's fuel-injected ones, but (combustion-wise) it's mostly because carburetors don't accurately feed the right total amount of fuel per amount of air over the wide range of operating conditions engines experience. Intake manifold heating does a good job of vaporizing the liquid fuel before it gets to the cylinder (once the engine is warm), but at the expense of a hot mixture that is less dense, and so it will produce less power.

Look at the engine efficiency issue this way: imagine you burn all the fuel (producing the maximum possible amount of heat), and some of that heat increases the pressure and causes the burnt gases to push the piston down the cylinder. That energy is the work that pushes your car. To maximize efficiency, you'd (ideally) want to insulate the cylinders to keep the pressure high as far down the cylinder as possible. Then you'd want to let the piston move down the cylinder until the exhaust gas temperature becomes equal to the outside air (meaning you've "extracted" nearly all its heat energy to push the piston). Altogether, this means you've lost no (heat) energy to the coolant or exhaust, and used nearly all of it to push the piston and propel the car. Very high efficiency!

Real engines do lose a lot of energy to the coolant (or you'd hurt the engine), and to the exhaust. But it's HEAT that's lost, NOT UNBURNT FUEL. Again, the fuel is almost completely burnt, as long as it's metered correctly and vaporized (again, carbureted engines vaporize fuel well, once they're warmed up).

By the way, my book (Physics for Gearheads) discusses energy issues in a way that non-engineers can understand, including how engines convert a fuel's heat to power. What works and what doesn't.

As a fellow physics lover, I agree that improving efficiency is a great goal, one that I've helped with much of my career. But what you are pursuing has been pursued in the past because it sounds good, but it is based on erroneous ideas. Compared to other avenues you could pursue, this one will unfortunately be a waste of your time.

 

[jack action]

I am using a stainless steel Shell & Tube Heat Exchanger, (3" X 14"), and I have plumbed exhaust tubes into the shell sides, with the system having it's own independent exhaust system. I am using a motorcycle carburetor to supply air and fuel. The Air/Fuel mixture flows through the 30 straight tubes, and then through a 2.5" 90,(elbow), into the Open Plenum Edelbrock intake manifold.

This doesn't seem to vastly differ from a design of an exhaust crossover where a chamber is filled with exhaust gases to create a hot spot to improve fuel vaporization in the intake manifold passages (HINT: Racers block these passages to improve performance of their engines).

Yes, I do, Mech_Engineer. Here are a few:

http://www.consumerenergycenter.org/transportation/consumer_tips/vehicle_energy_losses.html

https://www.fueleconomy.gov/feg/atv.shtml

http://ffden-2.phys.uaf.edu/102spring2002_web_projects/z.yates/zach's[/PLAIN] web project folder/eice - main.htm

In your 2nd reference, it is written:

Engine Losses: 68% - 72%
thermal, such as radiator, exhaust heat, etc. (58% - 62%)
combustion (3%)
pumping (4%)
friction (3%)

Doesn't it say that only 3% is lost because of combustion? A number similar to what @Mech_Engineer presented (3.4%)?

When they say «exhaust heat» loss, doesn't «heat» implies that the fuel was already burnt?

I'm only saying this because in your 3rd reference, there is a link (Click[/PLAIN] here for a diagram of power losses.) where they show the following image:

The 6% friction loss is clearly not related to combustion, but the rest is lost through «water heating» and «exhaust heat». Clearly, «water heating» means that the fuel has burnt and heated up the coolant, as it is impossible that unburnt fuel has escaped through the cooling system. Why would «exhaust heat» mean a different thing?

A comparison of the current Gas mileage of the automobile as opposed to the factory ratings, with a goal of quadrupling the factory gas mileage ratings.

Being realistic, do you think that if an engine manufacturer could lower their engines' fuel consumption by a factor of 4 by simply heating the fuel to vaporize it, they wouldn't have done it by now?

Even assuming your theory is right, you must - at the very least - admit that there must be downsides you haven't thought of.

We're talking about cars doing 120 mpg . Worst, if the fuel is completely burnt within the engine as you think it would, it means it could possibly makes 4 times the maximum power output it does today! There cannot be a worldwide conspiracy going on for over 100 years to keep this incredible (and simple) fuel saving method to not be realized by at least one racing guy at the local race track somewhere on this planet.

By the way, here's what engines that do not burn all their fuel look like (In these cases, the valve overlap is so large that at idle, part of the air-fuel mixture goes directly to the exhaust port during the intake stroke; This is not a problem at high rpm, thus no more flames in the exhaust system):

​

 

[Terrysv]

It sounds like the issue here is of unburnt fuel in a combustion chamber, let’s try a differential diagnosis. Combustion is like sitting on a stool with three legs. If one leg of the stool is weak or short the deficiency is easy to find. Fuel, oxygen and heat combustion is a three part chemical reaction. A diesel can produce black smoke. The black smoke is unburnt fuel. If this diesel fuel will not burn in liquid form and it doesn’t have time to vaporize then all diesels will produce black smoke all the time.

The electronic ignition in my car has sensors measuring the exhaust in order to keep the air fuel ratio constant. Perhaps some of the unburnt fuel is coming from the ignition system making adjustments like sudden acceleration or the choke function at start up.

https://en.wikipedia.org/wiki/Oxygen_sensor

 

[Ketch22]

Hello, Can someone tell me the optimum stoichiometric air/fuel ratio of gasoline VAPOR? I know that with liquid gasoline the optimum stoichiometric air/fuel ratio is 14.7 parts ambient air to 1 part gasoline. .

Michael, looks like my late arrival in his thread is a little late but let me throw some stuff in partially in support of you pursuit. The Stoichiometric ratio is an elusive thing. While perfection is easy to determine mathematically (it measures the number of molecules of gasoline to the molecules of air, no difference if it is vapor or liquid). What is known at this time is that at normal idle for normal engines they tend to hunt a little at perfect thus the mixture is mostly adjusted a little rich typically only about 14.3- 14.5. Once off idle the engine runs ok with moderate power if it is run somewhat lean. Lean burns increase the temperatures, marginally decrease the power, and dramatically increase the production of pollutants primarily oxides of nitrogen. With modern pollution controls it is still possible to run your engine at 15.3- 15.6 ratios. One must be quite careful. The combustion temperatures can go up severally. A carbureted engine can suffer from a condition often called lean misfire and it will melt pistons. At a slight increase of demand for power above a "lean cruise condition" it is important that ration get back to Stoich, the power will be reduced noticeably if not. Best performance is realized from slightly off idle ( around 1000 rpm on an old V8) to close to mid rpm ( somewhere in the vicinity of 4000rpm on a V8). As you cross this next threshold the efficiency of the combustion begins to overwhelm the cooling capabilities. In an old style engine the only conduction path for cooling pistons was via ring contact, newer engines are including oil spray jets, increased contact patch and various other methods. Even so Combustion heat cannot be conducted fast enough to save the engine. As there is still RPM available and power capabilities it is common to richen the mixture and drive down the temperatures. This also helps with the spark timing as it also can not be timed appropriately at elevated RPM. The ratio in this range is usually progressive. Prior to Thermal disadvantage point it will start to richen and it will usually be near 12.2:1 by valve float (just as a side note this is even more pronounced in a forced induction engine. At close to 2 bar intake manifold pressure the ratio will be at 11.5 or occasionally richer by the time the engine is 85 percent to valve float.

It is the high power demand points and the idle enrichment that drive up the uncombusted fuel. If you could spot analyze a modern engine at only stable low power cruise they burn very clean. It is the other points of having a usable engine that create the inefficiencys you are pursuing. Now each engine design adds it's own charecteristics and each driver their idiosynchrasies and it is real hard to "win." This is why as the 70's were closing and moving into the 80's the switch was made to fuel injection. The Engine control module takes many inputs and attempts to determine what the driver is trying to do. It then delivers the right ratio to achieve the perceived goal. This is something a carburetor is not capable of doing.

My suggestion to you would be to narrow your search significantly. You can make a very efficient engine but it's performance will be low at best. You can build a high performance one but it will not be fuel efficient, (the nitro burners I once worked on consumed 17 gallons in a quarter mile, ugh).

By the way one should also find a source of pure gasoline or start over. If you are in the US almost everyone is burning "Oxygenated fuel" or E85. These both are blended with Ethanol. It stretches the fuel however the alcohol requires a completely different ratio and now all numbers are off and it changes depending on the blend. Here again a fuel injected engine can compensate but the carburetor can not.

 

[Vedward]

The Stoichiometric ratio comes from the amount of oxygen needed to combine with all the carbon (to make CO2) and hydrogen (to make H2O) in the fuel on a theoretical basis, then since air is 22% oxygen, 78% nitrogen, the amount of air needs to be adjusted accordingly.

I thought there needs to be some excess oxygen for best combustion. I have only experience with fuel injected railroad engines, so I may be wrong.

 

[Vedward]

One other thing, I've learned internal combustion engines (using Pistons ) only get 33% efficiencies, maybe a little more, of the energy of the fuel to the output. Only turbine with extra recovery systems can be higher than that.

 

[Ketch22]

I have only experience with fuel injected railroad engines, so I may be wrong.

You are exactly right on the basis of the ratio although speaking in general numbers which is kind of where this thread is at right now. There is a little confusion I think. In railroad engines I think they are almost all Diesel. I do not know of any gasoline engines and only a few experimental Natural gas. In a compression ignition engine there is always full air provided. The throttle controls the amount of fuel injected and the combustion utilizes whatever it needs.
In a spark ignition engine both fuel and air are metered into the cylinder and the ratio needs to be adjusted according to demand. Yes a little extra oxygen helps but that also increases temperatures and increases emissions. On a railroad engine where a bit of weight to compensate would not be an issue it is not to bad. On an Automobile it would be detrimental.